1. Technical Field
The present invention relates to a light emitting device and, more particularly, to a light emitting device using a double-sided electrode type semiconductor light emitting element.
2. Related Art
In JP-A-2011-228366, a light emitting device is disclosed which includes a semiconductor light emitting element, first and second electrodes respectively provided on the front and rear surfaces of the semiconductor light emitting element, first and second lead wires respectively connected to the first and second electrodes, and a glass for sealing the periphery of a portion of the first and second lead wires and the semiconductor light emitting element.
In JP-A-2007-207895, a light emitting device is disclosed which includes a container having a recessed opening made of an inorganic translucent material, a light emitting element accommodated in the recessed opening via a glass bonding material, a lid made of an inorganic translucent material and closing the recessed opening, first and second electrodes respectively formed on the upper and lower surfaces of the light emitting element, a first external connection conductor and a second external connection conductor. The first external connection conductor is conductively connected to the first electrode and penetrates the container. A portion of the first external connection conductor is exposed on the surface of the container. The second external connection conductor is conductively connected to the second electrode and penetrates the lid. A portion of the second external connection conductor is exposed on the surface of the lid.
Conventionally, there has been known a light emitting device which includes a semiconductor light emitting element mounted on an inner bottom surface of an opening of a package and a lead frame insert-molded to the package.
In this light emitting device, a wire bonding method of connecting a bonding pad formed on the surface of the semiconductor light emitting element with the lead frame by a bonding wire has been used in order to electrically connect the semiconductor light emitting element with the lead frame.
However, this light emitting device has the following disadvantages.
(a) Since the dimensions of the semiconductor light emitting element are defined by the bonding pad, it is difficult to miniaturize the semiconductor light emitting element.
(b) Since the dimensions of the opening of the package are defined by a bonding capillary, it is difficult to miniaturize the opening of the package.
(c) Adhesive made of a synthetic resin material is used in order to mount the semiconductor light emitting element on the inner bottom surface of the opening of the package. However, since the thermal conductivity of the adhesive is low, the heat dissipation efficiency of heat generated by the semiconductor light emitting element is low.
(d) Although an inner wall surface of the opening of the package is a reflective part (reflector), the light emitted from a side wall surface of the semiconductor light emitting element is transmitted through the reflective part. Accordingly, the light is not emitted from the opening and therefore the light emission efficiency is low.
In the technique disclosed in JP-A-2011-228366 or JP-A-2007-207895, a double-sided electrode type semiconductor light emitting element is used in which electrodes are formed on both front and rear surfaces and respective lead wires or respective external connection conductors are directly connected to respective electrodes.
Namely, since the technique disclosed in JP-A-2011-228366 or JP-A-2007-207895 does not use a wire bonding method, it is possible to avoid the disadvantages of the (a) and (b).
Further, since, in the technique disclosed in JP-A-2011-228366 or JP-A-2007-207895, the heat generated by the semiconductor light emitting element can be dissipated to the lead wires or the external connection conductors from the electrodes on both front and rear surfaces, it is possible to avoid the disadvantage of the (c).
Meanwhile, recently, a demand for a side-view type light emitting device (side light emitting device) has increased, as a thin light emitting device used for a backlight light source or the like of a liquid crystal display. In the side-view type light emitting device, thinning is especially required.
However, in the techniques disclosed in JP-A-2011-228366 or JP-A-2007-207895, it is difficult to cause the light emitting device to be thinner.
Further, in the side-view type light emitting device, a control for the directivity of light emitted from the side is required.
However, in the technique disclosed in JP-A-2011-228366 or JP-A-2007-207895, light is emitted in the circumferential direction of the entire side wall surface of the semiconductor light emitting element and a configuration corresponding to the reflective part is not provided. Accordingly, the disadvantage of the (d) is removed but it is difficult to control the directivity of the emitted light.
Therefore, a thin light emitting device preferred for the side-view type is required in which the directivity of the light emitted from the side can be controlled.
The present invention has been made to satisfy the above-described demands and an object thereof is to provide a thin light emitting device with low cost in which the heat dissipation efficiency and light emission efficiency of the semiconductor light emitting element are high and the directivity of the light emitted from the side can be controlled.